CKAD Practice Question: Application Environment, Configuration and Security
This CKAD practice question tests your understanding of application environment, configuration and security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A developer wants to ensure that a container runs as a non-root user and the filesystem is read-only except for a tmpfs volume. Which fields should be set in the container's securityContext?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
runAsNonRoot: true and readOnlyRootFilesystem: true
Option C is correct because `runAsNonRoot: true` enforces that the container cannot run as the root user (UID 0), and `readOnlyRootFilesystem: true` makes the container's filesystem read-only except for volumes explicitly mounted as writable, such as a tmpfs volume. Together, these fields satisfy the requirement of a non-root container with a read-only filesystem except for a tmpfs mount.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
runAsUser: 1000 and readOnlyRootFilesystem: true
Why it's wrong here
runAsUser does not guarantee non-root; the user could be 0.
✗
runAsNonRoot: true and privileged: false
Why it's wrong here
privileged: false does not make filesystem read-only.
✓
runAsNonRoot: true and readOnlyRootFilesystem: true
Why this is correct
runAsNonRoot prevents running as root, and readOnlyRootFilesystem makes the root filesystem read-only.
Related concept
Read the scenario before looking for a memorised answer.
✗
allowPrivilegeEscalation: false and readOnlyRootFilesystem: true
Why it's wrong here
allowPrivilegeEscalation prevents privilege escalation but does not force non-root.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the distinction between `runAsUser` (which sets a UID but does not enforce non-root) and `runAsNonRoot` (which enforces non-root but does not set a UID), leading candidates to pick Option A when they only need to ensure non-root, not a specific UID.
Detailed technical explanation
How to think about this question
The `runAsNonRoot` field uses the container runtime's user namespace to verify that the container's primary process UID is not 0; if the image specifies a user other than root (e.g., via USER directive), the runtime will still reject the pod if the UID is 0. The `readOnlyRootFilesystem` field makes the root filesystem of the container immutable at the kernel level (via mount flags), but any volume mounts (including tmpfs) can be made writable by setting their `mountPropagation` or by using an `emptyDir` with `medium: Memory` for tmpfs-like behavior.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKAD question in full detail.
Application Environment, Configuration and Security — This question tests Application Environment, Configuration and Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: runAsNonRoot: true and readOnlyRootFilesystem: true — Option C is correct because `runAsNonRoot: true` enforces that the container cannot run as the root user (UID 0), and `readOnlyRootFilesystem: true` makes the container's filesystem read-only except for volumes explicitly mounted as writable, such as a tmpfs volume. Together, these fields satisfy the requirement of a non-root container with a read-only filesystem except for a tmpfs mount.
What should I do if I get this CKAD question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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